Syphilis appeared in Sweden in 1497. It was recognized as a sexually transmitted disease that rapidly spread in the upper classes and later to the poor. It ravaged the country in the eighteenth and nineteenth centuries. At that time the concept of venereal disease included all sexually transmitted diseases. Preventive measures were introduced. They were based on information, medical intervention and elimination of risk factors. Registration of hospitalised patients was introduced in the eighteenth century. The highest incidence of syphilis occurred during the First World War. In the last decade the incidence of sexually transmitted disorders has abruptly decreased. Thus the yearly incidence of gonorrhoea has decreased from 40,000 to 500 cases. The law demands contact tracing with obligatory testing. People who deliberately expose others to risk may be condemned to isolation for an unrestricted time. This legislation has probably contributed less to the successful containment than the fact that information on aids and sexually transmitted diseases has reached all the population, and made it aware of the risks and produced changed behaviour, especially among prostitutes, homosexual men and drug addicts.